This invention relates to a combinatorial weighing method and apparatus for weighing out agricultural products such as green peppers and potatoes, lifestock foodstuffs such as meat and broilers, perishable foods, fruits and fabricated parts. More particularly, the invention relates to a combinatorial weighing method and apparatus wherein a combination giving a total weight value within set allowable limits can be obtained in a short period of time even if a weight value, produced as an output by a weighing machine, fluctuates due to vibration or the like.
According to a combinatorial weighing apparatus which is known in the art, combinatorial weighing is carried out by weighing articles which have been introduced into a plurality of weighing machines, forming combinations of the weight values from the weighing machines, obtaining a combination (referred to as the "optimum combination") the total weight of which is equal to a target weight value or closest to the target weight value within set allowable limits, discharging the articles from the machines belonging to the combination obtained, subsequently replenishing the weighing machines which have discharged their articles with additional articles in order to prepare for the next combination, and continuing automatic weighing by repeating the foregoing operations.
In a combinatorial weighing apparatus of the foregoing type, a weight value from a weighing machine ordinarily stabilizes at a predetermined time t.sub.0 after introduction of the articles into the weighing machine. Accordingly, the weight value is read at a predetermined time t.sub.1 following stabilization to enable combinatorial processing at high precision. It should be noted, however, that the weighing machine output (weight value) will be unstable even at time t.sub.1, as shown in FIG. 2, if the articles are supplied to the weighing machine in a single mass, rather than as a steady flow, or if the weighing machine is subjected to external applied vibration. In such case, reading the weight value from the weighing machine at time t.sub.1, obtaining an optimum combination by performing a combinatorial computation using the weight value, and discharging the articles from the weighing machines belonging to the combination may result in a batch of discharged articles having a total weight which is outside the set allowable limits, namely a total weight which is too low or too high.
If a solution to the foregoing problem is sought by delaying the reading of the weight value in order to prevent the weighing apparatus from discharging a batch of articles outside the set allowable limits, the moment at which combinatorial processing starts will be delayed correspondingly. This would make it impossible to carry out combinatorial weighing at high speed.